An apparatus and method for providing a control signal in front of a vehicle moving along a track having an earth ground potential, with the vehicle having first and second low impedance interconnected collector shoes being coupled between a pair of signal rails and provided at respectively the front end and rear end of the vehicle. A first control signal is provided in front of the vehicle to control the desired operation of the vehicle and a second control signal is provided in the rear of the vehicle to control an undesired operation of the vehicle. An impedance member is provided, in a first conductive circuit on the vehicle or in a second conductive circuit associated with the track, to prevent the second control signal in front of the train from having a threshold level high enough to confuse the desired operation of the train.